PIC18F4550ESOSQTP datasheet(193/430 Pages) MICROCHIP

193 / 430 page

Preliminary

DS39632D-page 191

PIC18F2455/2550/4455/4550

18.3.3

READING FROM THE SPP

Reading from the SPP involves reading the SPPDATA

read operation. When the read is finished, indicated by

the SPPBUSY bit, the SPPDATA will be loaded with the

current data.

The following is an example read sequence:

Write the 4-bit address to the SPPEPS register.

The

SPP

automatically

starts

writing

the

address. If address write is not used then skip to

step 3.

Monitor the SPPBUSY bit to determine when the

address has been sent. The duration depends

on the wait states.

Read the data from the SPPDATA register; the

data from the previous read operation is

returned. The SPP automatically starts the read

cycle for the next read.

Monitor the SPPBUSY bit to determine when the

data has been read. The duration depends on

the wait states.

Go back to step 3 to read the current byte from

the SPP and start the next read cycle.

SPPEPS: SPP ENDPOINT ADDRESS AND STATUS REGISTER

R-0

U-0

R-0

R/W-0

RDSPP

WRSPP

—

SPPBUSY

ADDR3

ADDR2

ADDR1

ADDR0

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

bit 7

RDSPP: SPP Read Status bit (Valid when SPPCON<SPPOWN> = 1, USB)

= The last transaction was a read from the SPP

= The last transaction was not a read from the SPP

bit 6

WRSPP: SPP Write Status bit (Valid when SPPCON<SPPOWN> = 1, USB)

= The last transaction was a write to the SPP

= The last transaction was not a write to the SPP

bit 5

Unimplemented: Read as ‘0’

bit 4

SPPBUSY: SPP Handshaking Override bit

= The SPP is busy

= The SPP is ready to accept another read or write request

bit 3-0

ADDR3:ADDR0: SPP Endpoint Address bits

1111

= Endpoint Address 15

•

0001

0000

= Endpoint Address 0

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